The temperature in Bega rose 15 degrees in one hour on Tuesday morning, hitting 41 degrees just after noon (AEDT). Many areas of Sydney hit the 40s soon after.

Winds of more than 90km/h whipped through the NSW southern ranges, as 90 per cent of the state was rated severe fire risk or higher.

NSW Rural Fire Service Commissioner Shane Fitzsimmons said it was shaping up to be a long day for thousands of firefighters.

"Right across the state we are seeing fires breaching some of their containment lines, and we've also got fire agencies identifying new fires that are starting up under these hot, dry conditions," Mr Fitzsimmons told reporters.

"We've got a lot of daylight left and a lot of nighttime left under these conditions."

He said the combination of heat, wind and dryness - following a record four months of hot conditions - was making it easy for smouldering stumps and embers in existing fire grounds to blow into unburned country.

The weather bureau was predicting a cool change across much of NSW on Wednesday morning, with temperatures expected to stay in the 30s on Tuesday evening.

Meanwhile, a 22,000ha bushfire was burning out of control between Forcett and the Tasman Peninsula in southern Tasmania.

At 1pm (AEDT) the fire was impacting on the areas of Eaglehawk Neck, Pirates Bay, Doo Town, Old Jetty Road and Blowhole Road, and residents and tourists were evacuating under police escort.

Since the fires on the peninsula were first reported last Thursday more than 550 houses have been searched and no bodies found, despite concerns for people still unaccounted for.

Around 40 bushfires continue to burn across Tasmania, with uncontrolled blazes at Montumana in the northwest and Lake Repulse in the Derwent Valley.

In Victoria, a slow-moving 7000ha bushfire in the south-west was still active but no longer posed a threat to the Drik Drik and Dartmoor communities.

Prime Minister Julia Gillard, who is getting briefings on the emergency situation, said it was important people kept themselves safe and that they listened to local authorities and local warnings.

"The word catastrophic is being used for good reason," she told the Seven Network of the fire risk warning level.

Federal Opposition Leader Tony Abbott, who is a member of the Davidson Rural Fire Brigade, is on standby with his brigade on Sydney's bushfire-prone north shore.